2 bug fixes in editor views

2 bug fixes in editor views

* `WTForms` instances get `__init__`-ed with `defaults` as `kwargs`.
  The first arg is a `request.form` (which is what one must supply if
  this is a `POST` and must *not* supply otherwise).
  The content of that form (empty on `GET`) has higher priority than
  the defaults (which makes the user get an empty form).

* Fix `edit_profile()` to allow changing `location` from a non-blank
  value to blank (i.e. removing the location).

(cherry picked from commit 75f3e23b92392b9bd309fab4c1a52fd38d453627)